Energy storage devices are devices such as batteries, capacitors, hybrid or asymmetric batteries and so forth which store and supply electrical energy or a current. Energy storage devices comprise electrodes (a cathode and an anode) and an electrolyte, all housed within a housing. Other devices including electrodes are sensors in electronic and medical monitoring devices.
There are many types of energy storage devices available commercially, and energy storage devices come in different sizes and arrangements appropriate for particular applications. Most commonly, energy storage devices such as batteries for portable applications include a hard casing, typically formed from a metal, which contributes considerable weight and bulk to the device. Many such devices are cylindrical in configuration, and thus do not utilise space most efficiently for applications where space, weight and bulk are of major importance.
One application where space and weight is important is in the area of the inclusion of energy storage devices or sensors in garments, or in other objects that are worn or carried by humans. In the case of military applications, military personnel are required to have a source of electrical energy to operate equipment. In such applications, military personnel may be carrying the equipment and energy storage device for many days, and thus comfort, weight, bulk and safety are of critical importance. Other applications where these considerations are of importance are in the area of operating portable electronic devices, such as entertainment devices including MP3 players and radios, communication devices including mobile phones and radios, and medical monitoring devices including sensors.
It has been recognised by the applicant that a flexible energy storage device, which can be incorporated into a flexible article such as a garment, could provide many benefits in these applications compared to rigid energy storage devices. However, for such devices to be a possibility, the flexibility must not compromise the performance of the storage device. Moreover, the components of such devices such as the cathode need to enable a balance to be achieved between flexibility, mechanical stability, good cycling properties (such as a rapid charge and discharge) and a sufficiently high energy density.